GB2268112A

GB2268112A - Electric hand power tool

Info

Publication number: GB2268112A
Application number: GB9312735A
Authority: GB
Inventors: Manfred Buck; Siegfried Fehrle; Wilfried Kabatnik
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1992-06-24
Filing date: 1993-06-21
Publication date: 1994-01-05
Anticipated expiration: 2013-06-21
Also published as: GB2268112B; ITMI930515V0; ITMI930515U1; IT230302Y1; DE9208407U1; GB9312735D0

Abstract

To facilitate assembly and disassembly of the motor (2) in the event of repair, the motor pinion (10) of a hand power tool is supported firmly in the casing (16). A cylinder portion 7 of the motor shaft (4) of motor (2) is introduced into a longitudinal bore (13) of the motor pinion (10) in which it is engaged without play. Torque is transmitted via a toothing (14) on the pinion (10) and a mating toothing (6) on the motor shaft (4). A sealing ring (9) provides sealing relative to the electrical components of the motor (2). In a second embodiment motor shaft 104 beam a tapered end portion 107 on the central part of which is arranged a radially projecting mating toothing 106 which meshes with a toothing 114 of pinion 110. <IMAGE>

Description

Electric hand power tool Prior art The invention starts from an electrically driven hand power tool in accordance with the precharacterising clause of Claim 1. DE-AS 11 61 832 (= US 3 133 600) discloses a percussion drill of similar design for mining. There, the output end of the motor shaft is of hexagonal design and is inserted loosely into a bevel gear having a hexagonal internal profile. For its part, the bevel gear is supported in the casing. This arrangement has the disadvantage that, at high speeds of rotation, the motor shaft must additionally be supported on the output side if large unbalanced forces and vibrations are to be avoided. In addition, there is the risk that lubricants will pass out of the reduction gear, along the motor shaft and into the electrical part of the driving motor and will cause malfunctions there.

Advantages of the invention In contrast, the hand power tool according to the invention, having the characterising features of Claim 1, has the advantage that the motor shaft is supported reliably and without play in the output pinion and can be removed in a simple manner for assembly and for the purpose of servicing the motor without the need to disassemble the gear mechanism and readjust it upon assembly.

Advantageous further developments and improvements of the hand power tool disclosed in Claim 1 are possible by virtue of the measures presented in the dependent claims. It is particularly advantageous to seal the motor shaft relative to the pinion, providing reliable protection for the motor against contamination. To protect the sealing ring, it is furthermore advantageous to arrange the latter ahead of the toothing, as viewed from the motor, allowing the lubricants for the pinion to act on the toothing as well. The sealing ring has the further advantage that it has a damping effect on the toothing between the shaft and the pinion during the starting of the motor.

Drawing Two exemplary embodiments of the invention are depicted in the drawing and explained in greater detail in the description which follows. Figure 1 shows a crosssection through a hand power tool and Figure 2 shows the connection between the shaft and the pinion in a second exemplary embodiment.

Description of the exemplary embodiments Of an electric hand power tool, Figure 1 shows only the area around the driving motor 2. On the collector side, this is supported in a rolling bearing in a casing 3. The motor shaft 4 projects from the motor 2 on the opposite side. A fan impeller 5 is slipped onto the motor shaft 4 for the purpose of cooling. Adjoining the fan impeller 5, the motor shaft 4 is tapered and bears a hexagon 6. An end portion 7 of the motor shaft 4 tapers again relative to the hexagon 6 and has a circular crosssection. A sealing ring 9, preferably made of rubber, is inserted into a circumferential groove 8 in the end portion 7.

The end portion 7 is inserted into a pinion 10 having a shank 11 and bevel toothing 12. For this purpose, the pinion 10 has a smooth longitudinal bore 13. At the motor-side end of the longitudinal bore 13, the pinion 10 is provided with a toothing 14 into which the motor-shaft hexagon 6, which acts as mating toothing, engages positively. In its untoothed region, the pinion 10 is supported by means of a rolling bearing 15 in a casing part 16. The rolling bearing 15 is press-fitted onto the shank 11 of the pinion 10 and hence connected to the latter in a play-free manner. On the casing side, the rolling bearing 15 rests against a collar 18 and, on the other side, is fixed axially by a retaining ring 19.

Sealing between the pinion 10 and casing part 16 is provided by a shaft seal 20.

The pinion 10 meshes by means of its bevel toothing 12 with a ring gear 22 secured on an intermediate shaft 23. The torque of the motor 2 is transmitted from the intermediate shaft 23, geared at the front end, via further gearing elements to the tool to be driven (not shown). The intermediate shaft is supported in a rolling bearing 24 which is seated in a bearing cover 25 mounted laterally on the casing 16.

In the assembly of the hand power tool, the entire gear mechanism including the intermediate shaft 23, the ring gear 22 and the pinion 10 but excluding the motor 2 and the motor shaft 4 can be preassembled. The backlash between the bevel toothing 12 and the ring gear 22 can be set definitively even at this early stage. The backlash is set in the process of mounting the bearing cover 25; - when the rolling bearing 24 is press-fitted onto the intermediate shaft 23, by inserting the washer 26; and - when the rolling bearing 24 is press-fitted in the bearing cover 25, by inserting a washer between the ring gear 22 and the rolling bearing 25.

Manufacturing and assembly tolerances in the mounting of the rolling bearing 15 in the casing 16 can be eliminated beforehand by means of a spring washer between the rolling bearing 15 and the retaining ring 19 or between the rolling bearing 15 and the collar 18.

Caulking of the rolling bearing 15 on the side of the collar 18 may also be considered. After final assembly of the gear mechanism, the motor 2 is pushed into the casing part 16 from below in Figure 1, the end portion 7 of the motor shaft 4 coming to lie in the longitudinal bore 13 of the pinion 10. The rotary engagement between the motor shaft 4 and the pinion 10 is provided by the toothings 6/14. To protect the electrical components of the motor 2, the motor shaft 4 is sealed off relative to the longitudinal bore 13 of the pinion 10 by means of the sealing ring 9. During the starting of the motor, the sealing ring 9 simultaneously acts as a damper between the motor shaft 4 and the pinion 10 since the toothings 6/14 have a certain backlash. Damping is desired in order to prevent any possible wear to the toothings 6/14.

In hand power tools with impact mechanisms, such as, for example, hammer drills, forces act on the gear mechanism in alternate directions of rotation and hence also give rise to alternating axial forces on the motor shaft 4. If this leads to axial displacements of the motor shaft because of the "movable bearing" 28 mounted in a rubber bush 27, the backlash in conventional constructions also changes and this can rapidly lead to the failure of the gear mechanism, particularly in the case of helically toothed bevel gears. This risk does not exist in the solution proposed, due to the axial decoupling of the motor shaft 4 and the pinion 10.

The second exemplary embodiment according to Figure 2 corresponds in all the parts not shown to the first exemplary embodiment. Similar parts are provided with reference numerals incremented by a hundred. The motor shaft 104 bears a tapered end portion 107, on the central part of which is arranged a radially projecting mating toothing 106, which meshes with a toothing 114 of the pinion 110. Formed below the mating toothing 106 is a circumferential groove 108 in which there is space for a sealing ring 109.

The pinion 110 is toothed over the major part of its longitudinal bore 113. As stated, the lower part of the toothing 114 meshes with the toothing 106 of the pinion. This serves to provide rotary engagement. The upper part of the toothing 114 has a tip diameter which is ground concentrically with the shank 111 and in which the cylindrical part of the motor shaft 107 is supported without play. A widened portion 125 is borne on the lower end of the shank 111, coaxially with the longitudinal bore 113, and the outer side of the sealing ring 109 rests against this widened portion. In this exemplary embodiment, it is particularly advantageous that the lubricants for the gear mechanism, which, in particular, also protect the bevel toothing 112, can penetrate into the longitudinal bore 113 and simultaneously lubricate the toothings 106/114. Viewed from the direction of the motor, the sealing ring 109 is situated ahead of the toothings 106, 114.

Claims

1. Electric hand power tool, in particular hammer drill or impact hammer, with a high-speed motor (2) which is supported in a casing (3) and, via a gear mechanism, drives a tool, in which arrangement a pinion (10) supported in a casing part (16) can be pushed onto the motor shaft (4) of the motor (2) and connected to it with rotational engagement, characterised in that the motor shaft (4) has a preferably cylindrical end portion (7), which engages without play in the pinion (10).

2. Hand power tool according to Claim 1, characterised in that the motor shaft (4) is sealed off relative to the pinion (10) by, in particular, a sealing ring (9) inserted into a circumferential groove (8) in the motor shaft (4).

3. Hand power tool according to Claim 1 or 2, characterised in that the pinion (10) has a toothing (14) only at its end facing the motor (2), and a mating toothing (6) of the motor shaft (4) engages positively in this toothing.

4. Hand power tool according to Claim 3, characterised in that the toothing (14) is an internal hexagon and the mating toothing (6) is an external hexagon.

5. Hand power tool according to Claim 3, characterised in that the toothing (14, 114) and the mating toothing (6, 106) each have the profile of a splined shaft.

6. Hand power tool according to one of the preceding claims, characterised in that, as viewed from the motor (2), the sealing ring (109) is situated ahead of the toothings (106/114), allowing the lubricants for the pinion (110) to act on the toothings (106/114) as well.

7. A hand power tool substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawings.